A keyboard is one of the widely-used computer peripheral devices. Via the keyboard, the user may input characters and instructions into a computer. FIG. 1 is a schematic top view illustrating the outward appearance of a conventional keyboard. The surface of the conventional keyboard 1 includes plural keys. These keys 10 are classified into several types, e.g. ordinary keys 101, numeric keys 102 and function keys 103. When one or more keys are depressed by a user, a corresponding signal is issued to the computer, and thus the computer executes a function corresponding to the depressed key or keys. For example, when an ordinary key 101 is depressed, a corresponding English letter or symbol is inputted into the computer. When a numeric key 102 is depressed, a corresponding number is inputted into the computer. In addition, the function keys 102 (F1˜F12) can be programmed to cause corresponding application programs to provide certain functions.
With the maturity of the computing technologies, the conventional keyboard that has basic functions fails to meet the requirements of various users. For this reason, the keyboard manufacturers make efforts in designing novel keyboards with diversified functions. Recently, an illuminated keyboard with an illuminating function has been disclosed. Since the outward appearance of the conventional illuminated keyboard is similar to the outward appearance of the conventional keyboard 1, only the inner structure of the conventional illuminated keyboard will be illustrated in more details as follows.
FIG. 2 is a schematic cross-sectional view illustrating a conventional illuminated keyboard. As shown in FIG. 2, the illuminated keyboard 2 comprises plural keys 20, a membrane switch circuit member 21, a light guide plate 22, an illumination module 23, a main circuit board 24, a reflector 25 and a base plate 26. The key 20 comprises a keycap 201, a key housing 202 and an elastic element 203. From top to bottom, the keycap 201, the key housing 202, the elastic element 203, the membrane switch circuit member 21, the light guide plate 22, the reflector 25 and the base plate 26 of the conventional illuminated keyboard 2 are sequentially shown. The main circuit board 24 is arranged at a second side of the membrane switch circuit member 21. The illumination module 23 is arranged at a first side of the membrane switch circuit member 21.
In the key 20, the keycap 201 is exposed outside the surface of the illuminated keyboard 2, so that the keycap 201 can be depressed by the user. The key housing 202 is used for fixing the keycap 201 and the elastic element 203. The elastic element 203 is penetrated through the key housing 202. In addition, both ends of the elastic element 203 are contacted with the keycap 201 and the membrane switch circuit member 21, respectively. The membrane switch circuit member 21 comprises an upper wiring board 211, a partition plate 212 and a lower wiring board 213. The upper wiring board 211, the partition plate 212 and the lower wiring board 213 are made of a transparent material. The transparent material includes for example polycarbonate (PC) or polyethylene (PE). The upper wiring board 211 has plural upper contacts 2111. The partition plate 212 is disposed under the upper wiring board 211, and comprises plural partition plate openings 2121 corresponding to the plural upper contacts 2111. The lower wiring board 213 is disposed under the partition plate 212, and comprises plural lower contacts 2131 corresponding to the plural upper contacts 2111. The plural lower contacts 2131 and the plural upper contacts 2111 are collectively defined as plural key intersections. Moreover, the membrane switch circuit member 21 is connected with the main circuit board 24 for transmitting first electric power and signals.
The illumination module 23 comprises an illumination circuit board 231 and plural light emitting diodes 232. For clarification and brevity, only a light emitting diode 232 is shown in the drawing. The illumination circuit board 231 is arranged at the first side of the membrane switch circuit member 21 for providing second electric power to the plural light emitting diodes 232. The light guide plate 22 has plural light-guiding zones 221. Each of the light-guiding zones 221 has plural light-guiding dots 2211. The light-guiding dots 2211 of each light-guiding zone 221 are uniformly distributed. In addition, each light-guiding zone 221 has plural gaps G. For clarification and brevity, only a gap G is shown in the drawing. The light-guiding dots 2211 are used for guiding the plural light beams to the keycaps 201. A process of forming the light-guiding dots 2211 will be illustrated as follows.
Firstly, a stencil with plural mesh openings is placed on a bottom surface 222 of the light guide plate 22. Then, light-guiding ink is poured to the stencil such that the light-guiding ink flows to the bottom surface 222 of the light guide plate 22 through the mesh openings. Then, the light-guiding ink is subject to a screen printing process, so that the light-guiding ink is printed on the bottom surface 222 of the light guide plate 22 to result in plural light-guiding dots 2211. As shown in FIG. 3, each of the light-guiding zones 221 that is formed by using the stencil with plural mesh openings comprises plural light-guiding dots 2211, wherein every two light-guiding dots 2211 are spaced from each other by the gap G.
As shown in FIG. 2, the reflector 25 of the illuminated keyboard 2 is disposed under the light guide plate 22 for reflecting the light beams. The base plate 26 is disposed under the reflector 25 for supporting the keycap 201, the key housing 202, the elastic element 203, the membrane switch circuit member 21, the light guide plate 22 and the reflector 25.
In the conventional illuminated keyboard 2, the keycap 201 has a light-transmissible region 2011. The light-transmissible region 2011 is located at a character region or a symbol region of the keycap 201. Moreover, the position of the light-transmissible region 2011 is aligned with a corresponding light-guiding zone 221 of the light guide plate 22. In such way, the light beams can be guided to the light-transmissible region 2011 through the light-guiding dots 2211 of the light-guiding zone 221, thereby illuminating the character region or the symbol region of the keycap 201. Consequently, the illuminating efficacy is achieved.
However, after the conventional illuminated keyboard 2 is used for a long time, some drawbacks occur. For example, since the plural keys 20 are frequently depressed, the light-guiding dots 2211 of the light guide plate 22 will be suffered from abrasion. Since there is a vacant space G between adjacent light-guiding dots 2211, the possibility of abrading the peripheries of the light-guiding dots 2211 will be increased. In addition, the abrasion at the periphery of the light-guiding zone 221 becomes more serious. Under this circumstance, these light-guiding dots 2211 fail to be uniformly distributed, and thus the light-guiding efficacy thereof is deteriorated.